1. Field of the Invention
The present invention relates to video signal combiners, and in particular, to analog video signal combiners.
2. Description of the Related Art
Video effects systems, including video effect generators and video combiners, are well known and widely used in the art. Generally, a video effects system receives at least two video input signals, with one selected for use as a video fill signal and the other selected for use as a video background signal. This selection involves another input signal, i.e. a key signal, which selectively keys the fill video over the background video. These video signals can then be processed in accordance with a number of well known video effects. For example, the fill video can be keyed onto the background video with perspective or rotational effects, or a video image can be constructed which appears to be a three-dimensional object with fill video occupying the faces of the object. While all of the foregoing, and much more, can be achieved with conventional video effects systems, many limitations have existed.
A problem with conventional video combiners involves the introduction of video highlights, such as gleams, to active video in real time. Conventional combiners require a complex key signal which must be defined in real time when seeking to introduce video highlights, or gleams, onto an output image which is being spatially transformed (e.g. rotated, given perspective or keyed into a three-dimensional image). This has required generation of a complex key signal.
Another problem with conventional video combiners involves layered keying of multiple video input signals. Conventional combiners have used layered keyers in which one keyed signal becomes the fill video signal for a subsequent keyer, and so on. This requires a great deal of hardware and complex circuit.
Another problem with conventional video combiners involves the establishing of fill video priority within a keyed output image. When multiple fill video images are combined on a single background and are simultaneously manipulated three-dimensionally, priority must be established to ensure that the "front" image remains in front and the "rear" image remains behind the front image. This priority must be dynamically adjusted in real time as the fill video images undergo their spatial (e.g. three-dimensional) transformations. Conventional systems, due to limited dynamic range for Z video information, often produce ragged or fuzzy image intersections during this Z data priority control.